In the patients with Barrett's esophagus, 12 biopsy specimens of the specialized intestinal metaplasia also will be taken using jumbo biopsy forceps at a level 1 cm distal to the squamocolumnar junction at baseline (6 biopsies will be used to establish the primary cell cultures and six will be used for the molecular analyses); 6 more biopsy specimens will be taken a t the same level immediately after bile acid perfusion for molecular analyses. All endoscopic procedures will be performed by Dr. S.J. Spechler.